1. Field of the Invention
This invention relates to a clamper of a paper feed tractor for clamping and fixing a pair of paper feed tractors for feeding perforated paper to a support shaft with a gap corresponding to the width of the perforated paper.
2. Description of the Prior Art
As a conventional clamper used for the purpose described above, a clamper shown in FIGS. 10 through 12 is known conventionally.
This clamper consists of a plurality of sleeve plates 42 projecting from the outer side surface of a frame 41 that constitutes a paper feed tractor, and a cylindrical clamp member 43 fitted rotatably to the outside of these sleeve plates 42.
When the clamp member 43 fitted to the outside of the sleeve plates 42 is rotated, the sleeve plates 42 undergo deflection, and fasten and clamp a support shaft 44.
Therefore, since the support shaft 44 is clamped only partially by the tips of the sleeve plates 42, the clamp force is small. Since the plurality of sleeve plates 42 undergo deflection to thereby generate the clamp force, the sleeve plates 42 are elongated and impede the reduction of size of the paper feed tractor.
Another clamper is shown in FIGS. 13 through 15.
This clamper has a structure wherein one of the ends of a U-shaped clamp member 45 is fixed to the outer side surface of a frame 41 and a lock lever 46 causes elastic deformation of the clamp member 45 so as to hold and clamp the support shaft 44.
Accordingly, the clamp member 45 is necessary as a separate component and increases the cost of production.
Since the center of a clamp portion 45a of the clamp member 45 deviates from the center of the support shaft 44, the paper feed tractor is likely to incline and to clamp the support shaft 44 due to this deviation.
Moreover, the point of application of the force (F) for causing deformation of the clamp member 45 by the lock lever 46 is spaced apart by a predetermined distance (m) from the center of the support shaft 44. Accordingly, a large moment occurs around the support shaft 44 at the time of clamping so that the paper feed tractor is clamped while its driving sprocket (not shown) is firmly pressed to a driving shaft (not shown). Consequently, the frictional resistance of the rotary portion of the driving shaft increases and the driving force increases uselessly.
Still another clamper is shown in FIGS. 16 to 18.
This clamper consists of a lock lever 47 having an application portion 47a which is eccentric with respect to the center of the support shaft 44 and a wall plate 48 positioned in the proximity of this lock lever 47 and projecting from the frame 41.
When the application portion 47a of the lock lever 47 is strongly pushed into the wall plate 48, its reaction pushes and clamps the support shaft 44 from the side portion.
Consequently, a turning moment around the center (O) in the transverse direction of the paper feed tractor acts on it so that the paper feed tractor is clamped while being inclined with respect to the support shaft 44. If the paper feed tractor is obliquely clamped to the support shaft 44 in this manner, the holes of perforated paper deviate from feed pins 50 of a feed belt 49 and normal paper feed cannot be carried out.